Examine source code of LeetCheck

{
  "manifest_version": 2,
  "name": "LeetCheck",
  "version": "1.0",
  "description": "Follow LeetCode users and track their progress.",
  "icons": {
    "32": "icons/32.png",
    "48": "icons/48.png",
    "96": "icons/96.png"
  },
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_icon": "icons/512.png",
    "default_title": "LeetCheck",
    "default_popup": "popup/index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{5c204935-b32a-4559-a23f-9d2ef3a82e40}"
    }
  }
}